Mars Global Surveyor
Mars Orbiter Camera (MOC)

A Look at "Active" and "Inactive" Martian Sand Dunes

MGS MOC Releases MOC2-199 to MOC2-204, 31 January 2000

Mars has been known for centuries to experience large dust storms, but
it wasn't until the Mariner 9 mission in 1971-1972 that pictures were
returned from the planet that showed sand dunes. Dunes are also good
evidence that the martian atmosphere is presently capable of
transporting loose sediment and depositing it elsewhere. Dunes are, in
fact, deposits of sand that have accumulated usually over periods
measured in thousands of years. Mars Global Surveyor (MGS) Mars
Orbiter Camera (MOC) images obtained since September 1997 provide new
clues about martian dune activity. MOC has found that
some dunes appear to be moderately active today, but they do not
appear to have moved downwind since the Viking missions more than 20
years ago. MOC also finds some sand dune fields that appear to be
inactive because the dunes are either covered by dust and landslide
debris, or cemented and eroded into ridged and grooved terrain, or
because they have many old impact craters on them. The six sets of
pictures presented here show the variety of dunes from recently-active
to solidified and cratered. These pictures were taken at various times
throughout the MGS MOC mission.